The Institute for Terrestrial and Planetary Atmospheres (ITPA) invites a distinguished scholar each year to present a seminar to honor the contributions of Distinguished Professor Emeritus Robert D. Cess to the development of atmospheric sciences at Stony Brook University. Dr. Isaac Held from the Geophysical Fluid Dynamics Laboratory (GFDL) at Princeton University is the Distinguished Cess Lecturer for 2017.

Dr. Held presented his Cess seminar on “Theories for the Poleward Heat Flux in the Atmosphere: History and Current Status” at SoMAS on Wednesday, April 19, 2016.

Abstract: The equator-to-pole temperature gradient on Earth is in large part controlled by the heat transport due to transient eddies in midlatitudes — the same eddies responsible for highs and lows familiar from weather maps.  I will discuss a class of theories for the magnitude of this eddy heat flux that rely on a picture of the flux as turbulent diffusion, with a diffusivity that can be understood, in turn, by understanding how eddy length and time scales are controlled. I will focus in particular on the evolution of our understanding of eddy length scales — from the idea, originating in linear theory, that this length scale is proportional to the radius of deformation, to theories that point to the centrality of the Rhines scale, in which the eddy length scale is tightly coupled to the the eddy kinetic energy.  The role of idealized atmospheric models in this evolution will be emphasized.